Is there a key command to drag a tab to another area? It's needed when thumbnails are present

I like to have anything to a hundred or more tabs open at one time from numerous sites so I'm using the tab stacking.

I noticed that when the thumbnails were on and the tab gets stacked that I can no longer move the tab to a different part of the tab screen. I've had to remove the thumbnails in order to move the tab. Is there a simple key command or another way this could be addressed?

I have lost count of the number of issues caused by people opening hundreds of tabs.

Which should bring you to the logical conclusion that there is indeed a problem that needs to be solved at some point.

Posting advice here how to do it different, while appreciated, does not really help, simply because 90+% of all Vivaldi Users don't read in this forum and even more people never stumble upon any of the threads like this. Just look at the numbers.

Admittedly 90+% of the users probably do not have the problem at all, because in my purely anecdotal experience most of them rarely, if ever, use tab stacks or open enough tabs to get into such problems ...

... but from the beginning Vivaldi was meant to cope with power users to and those do strange things to the poor thing.

In my opinion, twenty is plenty, thirty is dirty, and forty is naughty.

As you wrote, it is your opinion.
Mind that every new window needs about 70MB of extra RAM for its process. If you split e.g. 100 tabs into 5 windows, you need unnecessary 350MB extra, which can be an issue sometimes.
I am aware that there are ways to mitigate that but that is not a point because the majority of users does not know how to do that.

The fix for the problem is similar to the way Opera Presto did it:
Add a scrollbar to the tab stack preview and restrict the maximum size to the dimensions of the browser window minus some margin, which is basically some lines of added CSS and/or some small changes to the React code.

Which should bring you to the logical conclusion that there is indeed a problem that needs to be solved at some point.

Yes. The conclusion that it brings me to is that some users open far too many tabs. Since the majority of users do not, the best solution is to improve sessions and educate users rather than trying to solve all of the many problems associated with opening 100s of tabs.

Fixing the tab preview problem may be simple, but controlling RAM usage, tab hibernation, program startup times, and crash recovering, etc., are not.

Not only does opening 100s of tabs create lots of issues with system requirements, it also adds to the number of issues with the GUI, how to manage and locate tabs in this forest of tabs.

Since the majority of users do not, the best solution is to improve sessions and educate users rather than trying to solve all of the many problems associated with opening 100s of tabs.

So you are implying that users who open hundreds of tabs are not educated enough? That would be a big claim. I doubt it would stand a reality check.

Not only does opening 100s of tabs create lots of issues with system requirements,

8GB RAM and a 7 year old CPU is enough to easily keep 100 tabs active and several hundred in hibernated mode. Been there done that.
Additionally the command line switch
--process-per-site
drastically reduces the RAM load. See, I am educated enough to handle such numbers and I believe others are too.

it also adds to the number of issues with the GUI, how to manage and locate tabs in this forest of tabs.

F2 is your friend if you really need to search for a tab. If you don't use horizontal tabs, you can scroll and read the titles. If you open tabs next to each other and don't create a mess by opening all at the end, they can be kept neatly organized. There are multiple ways to keep tabs organized in one single window, so even that point you bring forward is moot, simply because you can do that in Vivaldi, no matter if you like it or not.

My conclusion:
If someone can't handle many tabs, he should not open many tabs. I am fine with that.

So you are implying that users who open hundreds of tabs are not educated enough?

Yes. That is backed up by the rest of your points. You have found out how to work around the problems of opening lots of tabs, so those who don't know these techniques need to be educated about how to get the best out of the browser.

Throwing endless development resources at a problem does not solve it. Providing tips (education) and minor improvements to sessions or scrolling of the previews is much easier.